1. Field of the Invention
This invention relates to a rocker pin type continuously variable transmission (CVT) chain.
2. Prior Art
A typical CVT chain is shown in FIG. 1, and generally comprises a pair of pulleys P1 and P2 mounted on a driving shaft D and a driven shaft F, respectively; and, a plurality of frictionally driven blocks B connected by means of an endless chain C entrained on said pulleys. Each of the pulleys has opposing conical surfaces S1, S1 and S2, S2 respectively. If the distance between the respective conical surfaces of either or both pulleys is changed, the contact position of the frictionally driven blocks relative to each conical surface is also changed, thereby changing the effective diameter of one or both of the pulleys. The resulting structure is commonly referred to as a "continuously variable transmission".
CVT chains are generally classified into rocker pin types and round pin types. Rocker pin type CVT chains are widely used to form so-called silent chains.
A conventional rocker pin type CVT chain is disclosed in U.S. Pat. No. 4,507,106, wherein the load transmitting surface of a rocker pin is formed by a series of continuous surface elements or portions of arcuate convex planes having different curvatures. On the other hand, the corresponding load transmitting surface of the bore of link plates into which the rocker pins are inserted is formed by a series of complimentary arcuate concave surface elements having different curvatures; and, the complimentary surface elements are adapted to closely fit each other.
The above-mentioned patent teaches that a close fit between the surfaces of the rocker pin and the link plate is hard to achieve because of the necessary manufacturing tolerances. Manufacturing to very close tolerances significantly increases the costs of production.
Moreover, a point or local contact between the load transmitting surfaces of the rocker pin and the link plate is unavoidable, which causes rapid fatigue in, and premature failure, of the link plate.